Branch chained polynitrodiols

ABSTRACT

Energetic branched polynitrodiols of the formula ##STR1## wherein Z is --C(NO 2 ) 3 , --CF(NO 2 ) 2 ,  --C(NO 2 ).su CH 3 , or --N(NO 2 )CH 3 , and a method of preparation. These diols are useful as components of energetic binders for plastic-bonded explosives.

BACKGROUND OF THE INVENTION

This invention relates to alcohols and more particularly to energeticpolynitroakyldiols.

The chief promise of energetic polynitrodiols for practical explosiveapplications are as monomers for the synthesis of hydroxy terminedprepolymers. In practice, the prepolymers are mixed with a solidexplosive,

    HOCH.sub.2 . . . CH.sub.2 OH+X.sub.2 R♯HO[CH.sub.2 . . . CH.sub.2 ORO--CH.sub.2 . . . CH.sub.2 ].sub.n OH

ex., RDX or HMX, an energetic plasticizer and isocyanate curing agents.The liquid slurry is then cast into a suitable mold and cured to form arubbery matrix which not only binds the solid explosive and defines theshape, but also contributes energy to the final composition.

The most attractive diols from the standpoint of energy and availabilityare 2,2-dinitro-1,3-propanediol (A-diol) and2,2,8,8-tetranitro-4,6-dioxa-1,9-nonanediol (DINOL). Both of thesediols, as is the case with the majority of known polynitromonols, aresubstituted with nitro groups in the beta-position. Alcohols of thistype are easily prepared by the addition of the respectivenitrocarbanion to formaldehyde (Henry reaction). Unfortunately, however,##STR2## this reaction is reversible in the presence of even mild basesand the resultant nitrocarbanion is subject to side reactions anddecomposition over ##STR3## varying periods of time.

Energetic polymers that contain unreacted beta-nitro alcohol end groupsare also subject to the reverse Henry reaction and under the conditionsof isocyanate curing wherein basic urethane linkages are formed,decomposition can and does occur. This leads to poor thermal stabilityand aging characteristics. This is undoubtedly the reason why AFNOL, anenergetic polymer, formed from pimeloyl chloride and DINOL wasultimately rejected as a candidate energetic polymer.

For this reason, a considerable effort has been expended among differentgroups to prepare energetic diols that are not subject to deformylationunder basic conditions. These have been without exception straight chaindiols, which generally, though not always, contain both nitramine andgem dinitro groups on the backbone. These structural characteristicslead to hard prepolymers with poor solubilities in the energeticplasticizers used in the explosive compositions. This type of diolappears to be of limited usefulness.

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide new energeticpolynitrodiols.

Another object of this invention is to provide new polynitrodiols whichare useful as components of energetic polymers.

A further object of this invention is to provide new polynitrodiolswhich are stable to deformylation (loss of formaldehyde).

Yet another object of this invention is to provide new branched chainpolynitrodiols which can improve the hydrolytic stability of energeticpolymers such as polyesters.

A still further object of this invention is to provide a method ofpreparing these new energetic polynitrodiols.

These and other objects of this invention are achieved by providingbranched polynitrodiols of the formula ##STR4## wherein Z is --C(NO₂)₃,--CF(NO₂)₂, --C(NO₂)₂ CH₃, or --N(NO₂)CH₃. These branched polynitrodiolsmay be prepared by the following method: ##STR5## wherein Z is asdefined above.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The energetic branched polynitroakyldiols of this invention are2-(trinitromethyl)-1,4-butanediol, HOCH₂ CH[C(NO₂)₃ ]CH₂ CH₂ OH;2-(fluorodinitromethyl)-1,4-butanediol, HOCH₂ CH[CF(NO₂)₂ ]CH₂ CH₂ OH;2-(1,1-dinitroethyl)-1,4-butanediol, HOCH₂ CH[C(NO₂)₂ CH₃ ]CH₂ CH₂ OH;and 2-(methylnitraza)-1,4-butanediol, HOCH₂ CH[N(NO₂)CH₃ ]CH₂ CH₂ OH.These diols can be used as monomers to produce energetic polymericbinders for use in plastic-bonded explosives.

These energetic branched polynitroalkyldiols offer advantages over priorart diols such as 2,2-dinitropropane-1,3-diol(A-diol), C(NO₂)₂ [CH₂OH]₂, and 4,6-dioxa-2,2,8,8-tetranitrononane-1,9-diol (DINOL), CH₂ [OCH₂C(NO₂)₂ CH₂ OH]₂, in the production of energetic polymeric binders.These branched polynitroalkyldiols produce polymers with end groupswhich do not undergo deformylation.

Another important feature of these diols is that the number of atoms inthe backbone is large enough to inhibit ring formation yet, short enoughso that a large number of oxygen linkages will be incorporated in thebackbone of the resultant polymer. These divalent oxygen linkages addflexibility to the polymer backbone and markedly enhance physicalproperties. Moreover, the fact the energetic groups are carried onbranches is important from the standpoint of physical properties sincenitroamino or gem-dinitro groups on the backbone of a prepolymer canmarkedly lower physical properties.

The reaction sequences for preparing these branched polynitroalkyl diolscan be summarized as follows: ##STR6## where Z is --C(NO₂)₃, --CF(NO₂)₂,--C(NO₂)₂ CH₃, or --N(NO₂)CH₃. The reaction of one mole oftrinitromethane with one mole of gamma-crotonolactone under the reactionconditions of example 1 produces 4-hydroxy-3-(trinitromethyl)butyricacid, gamma-lactone which is reduced by borane-tetrahydrofuran toproduce 2-(trinitromethyl)-1,4-butanediol as shown in example 3.Similarly, the reaction of one mole of fluorodinitromethane withgamma-crotonolactone under the reaction conditions of example 2 produces4-hydroxy-3-(fluorodinitromethyl)butric acid, gamma-lactone which isreduced by borane-tetrahydrofuran to produce2-(fluorodinitromethyl)-1,4-butanediol as shown in example 4. Using thesame procedure, 1,1-dinitroethane and gamma-crotonolactone can be usedto produce 2-(1,1-dinitroethyl)-1,4-butanediol and methyl nitramine andgamma-crotonolactone can be used to produce2-(methylnitraza)-1,4-butanediol.

The general nature of the invention having been set forth, the followingexamples are presented as specific illustrations thereof. It will beunderstood that the invention is not limited to these examples but issusceptible to various modifications that will be recognized by oneskilled in the art.

The gamma-crotonolactone starting material used in these examples wasprepared by the procedure disclosed by S. Takano and K. Ogasawara inSynthesis, 1974, (1), p. 42.

EXAMPLE 1 4-Hydroxy-3-(trinitromethyl)butyric acid, gamma-lactone##STR7##

A mixture of 7.5 g (0.089 mole) of gamma-crotonolactone, 56.7 g (0.124mole) of 33% aqueous nitroform and 32 ml of methanol was stirred in anoil bath at 72°-75° C. for 5 hr. The mixture was then cooled in an icebath to precipitate an oil which turned to a solid and was removed byfiltration and washed with cold water to give 13.7 g, mp 103°-105° C.The water wash precipitated more oil from the filtrate. After extractioninto methylene chloride, the oil was crystallyzed from methanol-water togive an additional 1.55 g of product [total yield of 15.25 g (73%)].Recrystallization from methanol-water raised the mp to 105°-106° C.; ¹ HNMR(CD₂ Cl₂): 2.74-3.36 (m,2H); 4.25-4.60 (m, 2H); 4.75-4.97 (m, 1H); IR(KBr): 1775 (shoulder at 1787) (C=0); 1600, 1590 (NO₂) cm⁻¹.

Anal. Calcd for C₅ H₅ N₃ O₈ : C, 25.54; H, 2.14; N, 17.87. Found: C,25.63; H, 2.13; N, 17.81.

EXAMPLE 2 4-Hydroxy-3-(fluorodinitromethyl)butyric acid, gamma-lactone##STR8##

A solution containing 16.5 g (0.196 mole) of gamma-crotonolactone and31.8 g (0.256 mole) of fluorodinitromethane in 100 ml of methylenechloride (protected by a drierite drying tube) was stirred in an icebath while 30.8 ml of pyridine was added in 3 ml portions over 5 min.The solution was stirred at ice bath temperature for 3 hr. before anadditional 8.9 ml of pyridine was added in 3 portions over 2 min. Afteran additional 3 hr. at 0° C., the solution was poured into a solutioncontaining 85 ml conc. hydrochloric acid diluted with 170 ml of water.The mixture was stirred vigorously at ambient temperature for 15 min.before the methylene chloride layer was separated, washed with water anddried over sodium sulfate. Removal of the methylene chloride gave 28.4 gof tan solid which was dissolved in 120 ml of hot chloroform. The hotsolution was stirred with 10 g of silica gel 60, then filtered and thesilica gel was washed with 120 ml of hot chloroform. Hexane was added tothe filtrate (at room temperature) to the cloud point. Cooling to -15°C. gave 21.9 g of white crystals, mp 58°-60° C. A second crop (4.6 g, mp57°-59° C.) raised the yield to 26.5 g (65%); ¹ H NMR (CDCl₃): 2.55-3.14(m, 2H); 3.97-4.88 (m, 3H); IR(KBr): 1800, 1766 (C=0), 1609, 1600(shoulder) (NO₂) cm⁻¹.

Anal. Calcd for C₅ H₅ N₂ FO₆ : C, 28.86; H, 2.42; N, 13.46; F, 9.13.Found: C, 28.95; H, 2.45; N, 13.18; F, 9.12.

EXAMPLE 3 2-(Trinitromethyl)-1,4-butanediol ##STR9##

A 1M solution of borane-THF (10 ML, 10 mmole) was stirred under anitrogen atmosphere in a cold water bath (15° C.) while 2.1 g (8.94mmole) of 4-hydroxy-3-(trinitromethyl)butyric acid, gamma-lactone wasadded. The solution was stirred at 25° C. for 1 hr. and then at 35°-37°C. for 3 days before it was cooled to room temperature and 1 ml of waterwas slowly added dropwise. Most of the THF was removed and the residuewas stirred with ether. The insoluble material (boric acid) was removedby filtration and the ether filtrate was extracted twice with water toremove remaining boric acid. The ether was removed to give 2.10 g (98%)of an oil which was essentially pure by TLC. An analytical sample wasobtained by chromatography on silica gel 60 with methylenechloride-acetone (80/20) as eluent: ¹ H NMR (CD₂ Cl₂) 1.90-2.12 (m, 2H),2.44 (broad OH), 3.60 (broad m, 1H), 3.93 (t, 2H), 4.23 (d, 2H); IR(film) 3700-3050 (OH), 1600 (NO₂) cm⁻¹.

Anal. Calcd for C₅ H₉ N₃ O₈ : C, 25.11; H, 3.79; N, 17.57. Found C,25.00; H, 3.86; N, 17.34.

EXAMPLE 4 2-(Fluorodinitromethyl)-1,4-butanediol ##STR10##

To a 1M solution of borane-THF (5 ml, 5 mmole) stirred under a nitrogenatmosphere in an ice bath was added 1.0 g (4.8 mmole) of4-hydroxy-3-(fluorodinitromethyl)butyric acid, gamma-lactone. Thesolution was then held in a water bath at 25°-28° C. for 24 hr. before 1ml of water was slowly added dropwise. The solution was poured into 15ml of water and extracted with ether to give 1.02 g (100%) of an oilwhich was essentially pure by TLC. Chromatography on silica gel 60 usingmethylene chloride-acetone (80/20) as eluent gave an analytical sample.¹ H NMR (CDCl₃) 1.70-1.93 (m, 2H), 2.36(OH), 3.34-3.97 (m, 5H); IR(film) 3700-3050 (OH), 1605 (NO₂) cm⁻¹.

Anal Calcd for C₅ H₉ N₂ FO₆ : C, 28.31; N, 4.28; N, 13.21: F, 8.96.Found: C, 28.04; H, 4.44; N, 12.81; F, 8.50.

Obviously many numerous modifications and variations of this inventionare possible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:
 1. A diol of the formula ##STR11## wherein Z isselected from the group consisting of --C(NO₂)₃, --CF(NO₂)₂, --C(NO₂)₂CH₃, and --N(NO₂)CH₃.
 2. The diol of claim 1 which is2-(trinitromethyl)-1,4-butanediol.
 3. The diol of claim 1 which is2-(fluorodinitromethyl)-1,4-butanediol.
 4. The diol of claim 1 which is2-(1,1-dinitroethyl)-1,4-butanediol.
 5. The diol of claim 1 which is2-(methylnitraza)-1,4-butanediol.
 6. A lactone of the formula ##STR12##wherein Z is selected from the group consisting of --C(NO₂)₃ --CF(NO₂)₂,--C(NO₂)₂ CH₃, and --N(NO₂)CH₃.
 7. The lactone of claim 6 wherein Z is--C(NO₂)₃.
 8. The lactone of claim 6 wherein Z is --CF(NO₂)₂.
 9. Thelactone of claim 6 wherein Z is --C(NO₂)₂ CH₃.
 10. The lactone of claim6 wherein Z is --N(NO₂)CH₃.
 11. A process for preparing a branchedpolynitrodiol comprising the following steps in order:(1) reacting onemole of a compound of the formula Z--H with one mole ofgamma-crotonolactone to produce a lactone of the formula ##STR13## (2)reducing the lactone produced in step (1) with borane-tetrahydrofuran toproduce the desired branched polynitrodiol of the formula ##STR14## (3)isolating the product branched polynitrodiol; wherein Z is selected fromthe group consisting of --C(NO₂)₃, --CF(NO₂)₂, --C(NO₂)₂ CH₃, and--N(NO₂)CH₃.